JP4748864B2 - Thermal head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a thermal head incorporated as a printer mechanism such as a factory memory, a word processor, and a video printer.
[0002]
[Prior art]
The thermal recording type image recording device is simple in structure and is advantageous for downsizing, weight reduction, and cost reduction. In addition, the recording sound is quiet and power consumption is low. Widely used for recording applications such as facsimile.
[0003]
A thermal head used in such a thermal recording system is electrically connected to a large number of heating elements 12 arranged in a straight line on the upper surface of a ceramic substrate 11 as shown in FIG. It has a structure in which a pair of electrodes 13a and 13b are attached in a predetermined pattern. While feeding a recording medium such as thermal paper onto the heating element 12, the heating element 12 is based on image data from the outside. It functions as a thermal head by selectively generating Joule heat individually and conducting the generated heat to a recording medium to form a predetermined print on the recording medium.
[0004]
In addition, the heating element 12 and the pair of electrodes 13a and 13b of the thermal head described above are patterned through the following process.
[0005]
First, a resistance thin film such as TaSiO that forms the heating element 12 and a metal thin film such as aluminum that forms the pair of electrodes 13a and 13b are sequentially coated on the upper surface of the ceramic substrate 11 by a conventionally known sputtering method or vacuum deposition method. A process of depositing and forming, and microfabricating the obtained laminated body by two photoetching, specifically, etching the resistive thin film and the metal thin film along the outer shape of the heating element 12 and the pair of electrodes 13a and 13b Thus, microfabrication is performed by the first photoetching for patterning the laminated body into a predetermined shape and the second photoetching for etching a part of the metal thin film to expose the lower resistance thin film, thereby the heating element 12 And the pair of electrodes 13a and 13b are patterned in a predetermined shape.
[0006]
[Problems to be solved by the invention]
However, according to the above-described conventional method for manufacturing a thermal head, the photo-etching is performed twice in order to pattern the heating element 12 and the pair of electrodes 13a and 13b. Prior to the first and second photoetching, a photoresist using a photosensitive resin was deposited and formed on the surface of the laminate as an etching mask. Therefore, after the first photoetching is finished and before the second photoetching is performed, the photoresist used in the first photoetching is peeled off from the surface of the metal thin film using a solvent or the like, The photosensitive resin must be reapplied to the exposed surface of the metal thin film, etc., and a second photo-etching photoresist must be newly deposited and formed. When a thermal head is manufactured by such a process, heat is generated. The pattern formation of the body 12 and the electrodes 13a and 13b takes a lot of time and has the disadvantage of poor productivity.
[0007]
The present invention has been devised in view of the above drawbacks, and an object thereof is to provide a method for manufacturing a thermal head that can simplify the manufacturing process and improve the productivity.
[0008]
[Means for Solving the Problems]
The thermal head of the present invention comprises a plurality of heating elements composed of resistive thin films arranged along the main scanning direction on the upper surface of the ceramic substrate, and a metal thin film formed on the resistive thin film. A thermal head formed by depositing and forming a pair of electrodes electrically connected to both ends, wherein the pair of electrodes are opposed to each other with a central portion in the main scanning direction facing the heating element. The tip portions of the pair of electrodes are narrowed toward the heat generator side and extend from both ends in the main scanning direction to the tip. Each of the edges is curved in a concave shape .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
1 is a plan view of a thermal head manufactured by the manufacturing method of the present invention, FIG. 2 is a sectional view of the thermal head of FIG. 1, 1 is a ceramic substrate, 3a is a heating element made of a resistive thin film, and 4a and 4b are metal A pair of electrodes made of a thin film.
[0011]
The ceramic substrate 1 is formed in a rectangular shape by a ceramic material such as alumina ceramics, and a glaze layer 2, a heating element 3, a pair of electrodes 4a, 4b, etc. are deposited and formed on the upper surface thereof, It functions as a support base material that supports these.
[0012]
When the ceramic substrate is made of alumina ceramic, it is manufactured by punching a ceramic green sheet formed using a ceramic raw material such as alumina, silica, magnesia or the like into a predetermined shape and firing it at a high temperature.
[0013]
Further, a glaze layer 2 is deposited on the entire top surface of the ceramic substrate 1, and a plurality of heating elements 3a and a pair of electrodes 4a and 4b are further coated on the top surface of the glaze layer 2 in a predetermined pattern. Wearing and forming.
[0014]
The glaze layer 2 is formed of a low heat conductive material such as glass, and accumulates a part of heat generated by the heating element 3a therein so that the temperature of the heating element 3a is a predetermined value required for printing in a short time. It acts as a heat storage layer that maintains the thermal response characteristics of the thermal head well so that the temperature is maintained.
[0015]
When the glaze layer 2 is made of glass, a predetermined glass paste obtained by adding and mixing an appropriate organic solvent or the like to glass powder is printed and applied to the entire upper surface of the ceramic substrate 1 by a conventionally known screen printing method or the like. It is formed by baking this at a high temperature.
[0016]
The plurality of heating elements 3a provided on the upper surface of the glaze layer 2 are linearly arranged in the main scanning direction at a density of, for example, 600 dpi (dot per inch) along one side of the ceramic substrate 1, For example, since it is formed by the resistive thin film 3 in which an electrical resistance material such as TaSiO, TiSiO, TaN, etc. is deposited to a thickness of 0.01 μm to 0.2 μm, power supply power is supplied via a pair of electrodes 4a, 4b described later. Is applied, Joule heat is generated, and a predetermined temperature necessary for forming a print is obtained.
[0017]
On the other hand, the pair of electrodes 4a and 4b are for supplying power to the heating element 3 in accordance with driving of a driver IC (not shown), and a common electrode 4a connected to all the heating elements 3a in common. It is composed of individual electrodes 4b individually connected to each heating element 3a, and for example, by a metal thin film 4 in which a metal such as aluminum (Al) or copper (Cu) is deposited to a thickness of 0.3 μm to 2.5 μm. Is formed.
[0018]
Further, the pair of electrodes 4a and 4b is patterned so that the tip portions facing each other with the heating element 3a extending to the heating element 3a side are approximately 10 μm to 50 μm at the center in the main scanning direction. As a result, the shape of each heating element 3a in plan view is such that the central area in the main scanning direction is narrower than the both end areas.
[0019]
A protective film 5 is further deposited on the surface of the heating element 3a and the pair of electrodes 4a and 4b, and the heating film 3a and the pair of electrodes 4a and 4b are covered with the protective film 5.
[0020]
The protective film 5 is made of an inorganic material having excellent wear resistance and corrosion resistance, such as silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), and sialon (Si—Al—O—N). The heating element 3a and the pair of electrodes 4a and 4b described above are effectively protected from corrosion due to contact with moisture or the like contained in the atmosphere and wear due to sliding contact of the recording medium.
[0021]
The protective film 5 employs, for example, a conventionally known sputtering method, and the above-described inorganic material is 3 μm to 10 μm on the upper surface of the glaze layer 2 or the like provided with the heating element 3a and the pair of electrodes 4a and 4b. It is formed by depositing on the thickness.
[0022]
Thus, the thermal head described above causes the heating elements 3a to selectively generate Joule heat based on image data from the outside while conveying a recording medium such as thermal paper onto the plurality of heating elements 3a. The generated heat is conducted to the recording medium to form a print on the recording medium, thereby functioning as a thermal head.
[0023]
Thermal head such a structure, the plan view shape of each heating element 3a is Ri narrow Nashitea than across regions as previously described in the central region of the main scanning direction, a pair of electrodes 4a, 4b are, fever across the body 3a 10 m to 50 m approximately at the center of the front end portion facing the main scanning direction, because is patterned so as to extend the heating element 3a side, during printing, to reduce the friction between the recording medium Therefore, it is possible to reduce the amount of generated paper waste, effectively prevent deterioration of print quality due to adhesion of paper waste, etc., and reduce the maintenance work associated with the removal of paper waste. There are advantages.
[0024]
Next, a method for patterning the heating element 3 and the pair of electrodes 4a and 4b of the thermal head described above on the ceramic substrate 1 will be described with reference to FIG.
[0025]
(1) First, a ceramic substrate 1 to which the glaze layer 2 is applied is prepared, and a laminate 6 composed of a resistance thin film 3 and a metal thin film 4 is formed on the upper surface thereof as shown in FIG.
[0026]
The resistive thin film 3 and the metal thin film 4 employ a conventionally well-known thin film forming technique such as sputtering or vacuum deposition, and a ceramic substrate on which an electrical resistance material such as TaSiO and a metal material such as Al are provided with a glaze layer 2 It is formed by sequentially depositing on the upper surface of 1.
[0027]
The thickness of the laminate 6 is set to 0.01 μm to 0.2 μm for the resistive thin film 3 and 0.3 μm to 2.5 μm for the metal thin film 4, for example.
[0028]
(2) Next, as shown in FIG. 3B, a conventionally well-known photolithography technique is employed, and a photoresist 7a made of a photosensitive resin is deposited and formed on the entire top surface of the laminate 6 described above.
[0029]
As the photosensitive resin, a positive photosensitive resin in which a portion irradiated with ultraviolet light is altered and removed in an exposure / development process is used, and a liquid photosensitive resin having such properties is used. It is applied to the upper surface of the laminate 6 by a conventionally known spin coat method, roll coat method or the like, dried, and then a predetermined pattern corresponding to the shape of the heating element 3a and the electrodes 4a and 4b shown in FIG. The photoresist 7a is formed by exposing and developing the photosensitive resin using the photomask.
[0030]
In this exposure process, the ultraviolet light irradiated onto the photosensitive resin through the above-described photomask is exposed with a reversal pattern of the heating element 3a and the electrodes 4a and 4b, and a photoresist obtained by developing the exposed pattern. The shape of 7a is a shape corresponding to the pattern of the heating element 3a and the electrodes 4a and 4b.
[0031]
(3) Next, as shown in FIG. 3 (c), a conventionally well-known etching technique is employed to continuously remove the metal thin film 4 and the resistive thin film 3 where the photoresist 7a is not present.
[0032]
In this etching, the laminate 6 is immersed in a strong acid-based etchant capable of etching both the metal thin film 4 and the resistive thin film 3, and the laminate 6 in a portion where the photoresist 7a does not exist is etched with the etchant. This is done by erosion / removal, whereby the laminate 6 is patterned along the outer shape of the heating element 3 and the pair of electrodes 4a, 4b.
[0033]
(4) Then, as shown in FIG. 3 (d), the photoresist 7a remaining on the laminate 6 is further exposed and developed into a pattern of the heating element 3a, and finally, as shown in FIG. 3 (e). Then, the metal thin film 4 in a portion where the photoresist 7a does not exist is removed by etching.
[0034]
In this exposure process, a photomask corresponding to the pattern of the heating element 3a is used, and in the subsequent etching process, a metal according to the pattern of the photoresist 7a ′ obtained by exposure and development using the above-described photomask. A part of the thin film 4 is etched away. That is, the surface of the metal thin film 4 exposed by the above-described exposure / development is brought into contact with a strong acid-based etchant different from the previous etchant to remove a part of the metal thin film 4, thereby The resistive thin film 3 is exposed to pattern a plurality of heating elements 3a, and the metal thin film 4 is separated into the common electrode 4a and the individual electrode 4b on both sides of the exposed portion, thereby obtaining a desired thermal head pattern.
[0035]
According to the manufacturing method of the present embodiment as described above, when patterning the heating element 3a and the pair of electrodes 4a and 4b, the laminate 6 composed of the resistance thin film 3 and the metal thin film 4 is formed into a single photosensitive resin 7. Since the heating element 3a and the pair of electrodes 4a and 4b are finely processed by exposing and developing in two stages, the photoresist 7a is peeled off halfway or a new photoresist is applied. This saves time and simplifies the pattern formation process of the heating element 3a and the pair of electrodes 4a and 4b. Therefore, the productivity of the thermal head is greatly improved.
[0036]
In addition, when the thermal head is manufactured by the above-described method, the shape of each heating element 3a in plan view is narrower in the central area in the main scanning direction than in the both end areas. This is the second time described in the step (4). This is because the corners of the electrodes 4a and 4b are eroded (side etching) from the side surface during the etching, whereby a thermal head that is easy to maintain with a reduced amount of paper waste is obtained.
[0037]
In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.
[0038]
For example, in the above-described embodiment, the photoresist 7a may be baked before performing the second etching in order to suppress the side etching of the metal thin film 4.
[0039]
【The invention's effect】
According to the present invention, when patterning the heating element and the pair of electrodes, a resistive thin film that forms the heating element and a metal thin film that forms the pair of electrodes are sequentially stacked, and a single film is deposited on the surface. By exposing and developing the photosensitive resin (photoresist) in two stages, the heating element and the pair of electrodes are microfabricated, so the photoresist can be peeled off halfway or a new photoresist can be applied Thus, the process of forming the pattern of the heating element and the pair of electrodes can be simplified and the productivity of the thermal head can be improved.
[Brief description of the drawings]
FIG. 1 is a plan view of a thermal head manufactured by a manufacturing method of the present invention.
FIG. 2 is a cross-sectional view of the thermal head of FIG.
FIGS. 3A to 3E are perspective views for each step for explaining the manufacturing method of the present invention. FIGS.
FIG. 4 is a plan view of a conventional thermal head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate, 3 ... Resistance thin film, 3a ... Heat generating body, 4 ... Metal thin film, 4a, 4b ... A pair of electrodes, 6 ... Laminated body, 7a, 7a '. ..Photoresist

Claims (1)

A plurality of heating elements composed of resistive thin films arranged along the main scanning direction on the upper surface of the ceramic substrate and a metal thin film formed on the resistive thin film, and are electrically connected to both ends of the heating element. A thermal head formed by depositing and forming a pair of electrodes,
The pair of electrodes are formed in a pattern so that the tip portions facing each other with the heating element interposed therebetween extend to the heating element side at the center in the main scanning direction ,
The heads of the pair of electrodes are narrower in width toward the heating element side, and edges extending from both ends in the main scanning direction to the tip are respectively curved in a concave shape. .

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